To enable the mobile communication network to provide new services, mobile station positioning technique needs to be introduced to determine the position of mobile stations. In a cellular mobile communication network, there are three basic positioning methods: 1) Time Of Arrival (TOA) positioning method, which obtains the distances from a mobile station to the corresponding base stations through measuring TOAs from the mobile station to three or more base stations, and then estimates the position of the mobile station through solving a set of circular equations; 2) Time Difference Of Arrival (TDOA) positioning method, which obtains the differences in distance from a mobile station to the corresponding base stations through measuring TDOAs from the mobile station to three or more base stations, and then estimates the position of the mobile station through solving a set of hyperbolic equations; 3) CELL Identifier (CELL-ID)+TOA positioning method, which firstly determines the position of the serving cell where the mobile station is located with the CELL-IDs configured by the network, and then further determines the position of the mobile station in the cell with the TOA from the mobile station to the serving base station.
However, in traditional mobile communication systems, to ensure normal communication between mobile stations and base stations, repeaters are deployed in some areas that can't be covered by base stations; a repeater is essentially a bidirectional radio frequency signal amplifier, which amplifies and forwards both uplink signals sent from a mobile station and downlink signals sent from a base station; as shown in FIG. 1, in the downlink direction, the donating antenna (antenna of the serving base station) picks up signals from the existing coverage area, filters out-of-band signals through a bandpass filter, amplifies the filtered signals through a power amplifier, and then resends the amplified signals to the area to be covered; in the uplink direction, signals from the mobile station in the coverage area are processed in a similar way and then sent to the corresponding base station; thus, signal transmission between the base station and the mobile station is implemented. The introduction of a repeater implements normal communication between the mobile station in the base station's coverage area and the base station.
The introduction of repeaters results in that the mobile stations in the coverage area of the repeater can't be positioned effectively. When a mobile station required to be positioned is in the coverage area of a repeater, for the TDOA positioning method, the TDOA positioning process will fail because of the number of detectable base stations being too small; even if enough base stations can be detected, there will be very big deviations in the measured values because the signals from the base stations are forwarded by the repeater; as a result, the measured TDOAs can't correctly reflect the differences in distance between different base stations and the mobile; if the measurement result is used for position estimation, there will be a very big deviation in the determined position of the mobile station; furthermore, the positioning system is unable to determine whether the mobile station is within coverage area of the repeater or not and whether the measurement result is affected by the repeater or not. Likewise, when the mobile station requested to be positioned is in coverage of the repeater, for the TOA+CELL-ID positioning method, there will be bigger errors in TOAs due to the time delay effect resulted from the repeater and the TOA positioning accuracy will be degraded severely; as the result, it is unable to positioned the mobile station accurately.